In a conventional technique, when performing image capturing by scanning a target object in a specific scanning direction (e.g., satellite observation using the orbit of an artificial satellite), an optical detector called a line CCD (Charge Coupled Device) is used, in which a plurality of light-receiving elements, each corresponding to one pixel, are arranged in a direction perpendicular to the scanning direction (see, for example, Patent Document 1).
Hereinafter, an image capturing method of the conventional technique by an image capturing apparatus using the line CCD will be described using the drawings.
FIG. 5 is a diagram showing a known satellite observation method.
As shown in FIG. 5, an artificial satellite which moves in an AT (Along Track) direction, which is a traveling direction of the satellite and also a scanning direction. The artificial satellite includes an image capturing apparatus which has a line CCD in which light-receiving elements are arranged in a CT (Cross Track) direction perpendicular to the orbit of the satellite.
After the image capturing is started, the image capturing apparatus moves in the AT direction in accordance with the movement of the artificial satellite. The light-receiving elements of the line CCD in the image capturing apparatus receive light from each corresponding image capturing range (i.e., light-receiving range from the target object by the light-receiving elements) and accumulate (electric) charge which is obtained by photoelectric conversion and corresponds to the amount of received light.
When the line CCD completes the scanning of an image capturing range corresponding to one pixel in the AT direction, the light-receiving elements each output the accumulated charge, and start light reception from the next image capturing range. Accordingly, the line CCD sequentially outputs electric charge corresponding to the amount of light from the image capturing range in the CT direction, where each image capturing range corresponds to one pixel in the AT direction.
If the output charge is converted into image information for the CT direction, and the sequentially-obtained image information is aligned in order of the image capturing time, then the image of the target object is obtained.